1. Field of the Invention
The present invention relates to a liquid crystal display comprising fewer signal lines for driving pixels.
2. Description of Related Art
FIG. 37 is an illustration showing the structure of a conventional liquid crystal display. In FIG. 37 symbol 1 denotes a liquid crystal panel in which r scanning lines of G1 to Gr and s signal lines of D1 to Ds are arranged like a matrix and thin-film transistors T, T, . . . are formed one at each intersection between the scanning lines G1 to Gr on one hand and the signal lines D1 to Ds on the other. Moreover, each liquid crystal layers L, L, . . . is driven by turning on/off each of the transistors T, T, . . . Furthermore, symbol 2 denotes a gate driver for driving the scanning lines G1 to Gr and 3 denotes a data driver for driving the signal lines D1 to Ds. FIG. 38 is an illustration showing the timing for driving the scanning lines G1 to Gr and the signal lines D1 to Ds.
In the case of the above structure, horizontal pixel lines are driven in order starting with the first line by successively turning on the scanning lines G1 to Gr and thereby, display is performed. Moreover, the pixel lines may be driven by the interlaced scanning method according to the NTSC standard.
Therefore, in the case of an active-matrix liquid crystal display having r scanning lines of G1 to Gr and s signal lines of D1 to Ds, a gate driver having r outputs and a data driver 3 having s outputs are necessary on the outside of the liquid crystal display 1. This is because carriers in amorphous silicon necessary for the thin-film transistors T, T, . . . have small mobility and thus, it is impossible to form a high-speed circuit for driving the scanning lines G1 to Gr or signal lines D1 to Ds in the liquid crystal panel 1.
To improve the definition of a display screen (improvement of resolution), increasing the number of the signal lines D1 to Ds causes pitch between terminal portions to narrow, the number of data drivers to increase, and power consumption to increase. An example of forming some functional pieces of a data driver with amorphous silicon is also reported. In this case, however, a complex external circuit to generate tens of multiplexing signals results in increased cost as a whole.
Moreover, to decrease power consumption, the voltage of a driver is lowered. Therefore, a method for reversing a counter electrode (common reversal driving) is used. In the case of this method, however, it is necessary to write signals at the same polarity under scanning. Therefore, the problem of crosstalk due to capacitive coupling between a signal line and a counter electrode is pointed out.
The present invention is made to solve the above problems and its object is to provide a liquid crystal display making it possible to avoid narrowing the pitch between terminal portions of a data driver by decreasing the number of signal lines and to reduce power consumption and cost.
Moreover, it is another object of the present invention to provide a liquid crystal display making it possible to prevent contrast from deteriorating and the crosstalk from increasing even if common reversal driving is used.